High-Current ESD Test of Advanced Triple Junction Solar Array Coupon

Abstract

Testing was conducted on an advanced triple junction (ATJ) coupon that was part of a risk reduction effort in the development of a high-powered solar array design by Space Systems/Loral, LLC (SSL). The ATJ coupon was a small, four-cell, two-string configuration that has served as the basic test coupon design used in previous SSL environmental aging campaigns. The coupon has many attributes of the flight design; e.g., substrate structure with graphite face sheets, integrated by-pass diodes, cell interconnects, room-temperature vulcanizing grout, and wire routing. The objective of this test was to evaluate the performance of the coupon after it is subjected to secondary arc testing at two string voltages (100 and 150 V) and four array currents (1.650, 2.000, 2.475, and 3.300 A). An external test circuit, unique to SSL solar array design, was built that simulates the effect of missing cells and strings in a full solar panel with special primary arc (PA) flashover circuitry. A total of 73 PAs were obtained that included seven temporary sustained arcs (TSAs) events. The durations of the TSAs ranged from $50~\mu \text{s}$ to 2.75 ms. All TSAs occurred at a string voltage of 150 V. Post-test large area pulsed solar simulator, Dark $I$ – $V$ , and by-pass diode tests showed that no degradation occurred due to the TSA events. In addition, the post-test insulation resistance measured was $>50~\text{G}\Omega $ between cells and substrate. These test results point toward a robust design for application to a high-current, high-power mission.